How far is DS emulation really?

I recently got roms of the DS Castlevania games and 3 DS emulators with their newest versions:
iDeaS, DeSmuME and No$GBA.
But not a single of them was actually able to play any of the roms.

Everywhere I go I heard DS emulation is already pretty far and at least some of the commercial games work.
Was that just Shenanigans or do you have to do more to get the games to work?

for one of the emulators (I think No$GBA) I could use 2 different bios, but I couldn't find any download link.

Would that make any difference or are they all still only able to play homebrew and demos?

no$gba is among the most accurate emulators out there, and many homebrew authors paid to get the debug-enabled build to test their creations. I'd try more than one specific .nds file before deciding that it's crap.

Also please read the DCEmu forum rules. This is not the place for piracy discussion.